/ˈsaɪ.mən/Simon /ˈɹoʊ.zən/Rosen

Senior ML Data Linguist at ServiceNow

I am a linguist specializing in phonetics, phonology, and prosody. Since 2023 I have worked on speech and voice AI evaluation at ServiceNow. I design TTS and voice agent evaluations, including multilingual vendor comparisons, write the rubrics and annotation guidelines behind them, and build the internal labeling tools our linguists use to run them.

I am co-first author of Beyond Naturalness (EMNLP 2026, Main Conference), a benchmark for evaluating TTS output on individual linguistic dimensions.

Voice sample · synthesized · 0:09
A short introduction synthesized with ElevenLabs, annotated: broadband spectrogram (0–5 kHz) with formants and pitch, and ToBI tone, IPA, word, and break-index tiers. Click a word or drag across a span to play it.

Experience

Senior ML Data Linguist

Feb 2026 – Present
ServiceNow, LUNAR team (Linguistic Unit for NLU Analysis & Research)
  • Co-designed a 10-dimension annotation schema that breaks TTS “naturalness” into word-level, prosodic, and paralinguistic dimensions, and built an 860-utterance benchmark labeled by trained linguist raters (EMNLP 2026, co-first author).
  • Compared eight automated speech evaluators (four MOS predictors, four audio-LLM judges) against human labels under four prompting conditions, MOS predictors mostly tracked acoustic signal quality, and audio-LLM judges caught some error types depending on the prompt. Neither reliably detected the full range of linguistic errors.
  • Designed and ran a multilingual TTS vendor comparison. Wrote test sentences drawn from ITSM and CSM language and text normalization edge cases (symbols, math, units, URLs), defined a rubric pairing holistic 1–5 ratings with per-category head-to-head judgments, and adapted it for Japanese with a native-speaker linguist.
  • Built a rating framework for AI voice agent conversations covering speech fluency, tool calling, task completion, and helpfulness, and wrote its annotation guidelines.
  • Ran the labeling efforts that produced human benchmarks for customer-facing voice fluency judges: wrote the guidelines, onboarded labelers, and presented results across agents, separating ASR-driven failures (such as repeated confirmations) from conversation-flow and voice-style problems.
  • Leading success labeling for document question answering and building the matching LLM judge.
  • Built and maintain the internal labeling tools used on these projects, and the team’s project-tracking app.

ML Data Linguist

Jan 2023 – Feb 2026
ServiceNow, LUNAR team
  • Wrote LLM-as-judge prompts and structured output schemas for internal evaluation tooling. Authored a prompt design guide that became the team reference, and led training sessions so product teams could build their own evaluations.
  • Cataloged recurring failure patterns (hallucination, under-specification, intent misclassification) and worked with ML engineers on prompt changes, retraining, and production model selection.
  • Built a ground-truth benchmark through paired human and model evaluation, and compared it against LLM-as-judge scores and automatic metrics to find where they disagreed.

Results from ServiceNow projects are internal, except those published in the paper below.

Publication

Beyond Naturalness: Probing Automated Text-to-Speech Evaluators on Linguistically Grounded Dimensions
Oluwanifemi Bamgbose*, Simon Rosen*, Jash Shah, Lindsay Devon Brin, Hoang H. Nguyen, Anke Koelzer, Rachel Hansen, Tara Bogavelli, Fanny Riols
EMNLP 2026, Main Conference · arXiv:2608.09930
*Equal contribution. I designed the annotation schema and led the annotation effort. The dataset, schema, and evaluation code are publicly released.

Skills

Speech and linguistics
Phonetics and phonology, prosody and tone, segmental and suprasegmental analysis, IPA transcription, acoustic analysis (Praat), forced alignment (Montreal Forced Aligner), pragmatics and discourse
Voice AI evaluation
TTS and ASR evaluation, TTS vendor comparison, text normalization test design, MOS predictor and audio-LLM judge benchmarking, voice agent conversation rating, failure taxonomies, LLM-as-judge design
Experiment design and statistics
Benchmark construction, rubric and annotation guideline design, inter-annotator agreement (Krippendorff’s α, bootstrap CIs), significance testing (Kendall’s τ, Mann–Whitney U, McNemar)
Engineering
Python (pandas, scikit-learn, statsmodels, matplotlib, seaborn), internal web tools, LLM applications and prompt engineering, structured output schemas, AI-assisted development (Claude Code), JSON, YAML, Git
Languages
English (fluent). University coursework in Mandarin Chinese and Indonesian.

Education

B.A. in Linguistics

2022
Princeton University

Thesis: Tone Sandhi and Constituency in Classifier Phrases Across Sinitic Languages

Coursework: Phonetics and phonology, syntax, semantics, pragmatics, Java programming, data structures and algorithms